Re: [patch] Mark rdtsc as sync only for netburst, not for core2

[Nick Piggin]

Arjan van de Ven wrote:
> Zhang, Yanmin wrote:
>
> > If it's a single processor, the go backwards issue doesn't exist. 
> > Below is
> > my patch based on Arjan's. It's against 2.6.19-rc5-mm2.
>
> Hi,
>
> this patch is incorrect
>
> > --- linux-2.6.19-rc5-mm2_arjan/arch/x86_64/kernel/setup.c    
> > 2006-11-29 10:41:21.000000000 +0800
> > +++ linux-2.6.19-rc5-mm2_arjan_fix/arch/x86_64/kernel/setup.c    
> > 2006-11-29 10:42:28.000000000 +0800
> > @@ -861,7 +861,7 @@ static void __cpuinit init_intel(struct          
> > set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
> >      if (c->x86 == 6)
> >          set_bit(X86_FEATURE_REP_GOOD, &c->x86_capability);
> > -    if (c->x86 == 15)
> > +    if (c->x86 == 15 && num_possible_cpus() != 1)
> >          set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
>
>
> first of all, you probably meant "|| num_possible_cpus() == 1"
>
> but second of all, the core2 cpus are dual core so.. .what does it bring 
> you at all?

I guess you could boot with a UP kernel or maxcpus=1?

--
SUSE Labs, Novell Inc.
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